George,
In all cases that I am considering both the V and I CCDs see a simultaneous
increase in brightness. It is not always necessarily the same increase in
each channel. We only measure stars which have detections at the same
location in the sky within 7 arc seconds made simultaneously with two
cameras. Same location in the sky does not mean same CCD pixel
coordinate. This rules out some kinds of electronic problems.
There are 4 million pixels. There are of order 20 cosmic ray hits on each
of the two CCDs during a typical exposure. The probability of a
simultaneous hit in the same star on the two chips is pretty low. I give
it 2 x 10E-11 but I have probably computed it wrong. This exceeds by a lot
the number of measurements in my catalog.
I tried to make this computation before on a different project and left out
a factorial in the numerator. Still, the probability is quite low, though
I suspect not as low as above.
Tom Droege
At 10:55 AM 5/18/03 -0500, you wrote:
>a cosmic ray hit into the star during the exposure
>
>george wm turner
>uits/rats @ indiana university
>812 855 5156
>
>On Sun, 18 May 2003, Tom Droege wrote:
>
> > Are there many stars that flash? I keep finding stars with one bright
> > point. I assume that these are airplanes flying by that happen to
> flash on
> > top of a measured star. This especially if the bright point is at a
> > slightly different position. But sometimes the bright point is at the
> > exact same position as all the others which I think unlikely for an
> airplane.
> >
> > Tom Droege
> >
> >
> >